1. Field of the Invention
The present invention relates to a variable voice rate apparatus for varying the rate of reproduced voice in, for example, video and audio apparatuses and medical instruments.
2. Description of the Related Art
The mainstream apparatuses that handle voice data or voice data related to video data have recently shifted from magnetic tapes to magnetic optical disks or semiconductor memories. Accordingly, the recording system has shifted from the analog system to the digital system.
Digital voice-recording systems facilitate the control of the rate of reproduced voice. Voice data can be caught more quickly by its quicker reproduction than the recording rate, or more slowly and clearly by its slower reproduction.
Some of the recent audio apparatuses and some voice reproduction application software for use in personal computers have a function for varying the rate of reproduced voice data, utilizing the features of digital voice data.
This function uses methods for controlling voice data based on the features of its waveform data. The methods include, for example, a method for uniformly shortening the time required for reproducing the waveform data of digitized voice data, and a method for generating, based on its waveform data, voice data whose reproduction time is shortened, and a method for intermittently skipping the reproduction of voice data. Further, a method is also included in which silent portions are detected in voice data, and the time required for reproducing the voice data is shortened by excluding the silent portions (see, for example, Published Japanese Patent No. 3219892, pages 4-9 and FIG. 1).
However, in the above-described conventional method for shortening the reproduction time of voice data, the rate of reproduction cannot be greatly increased, since no one can follow the reproduced data if the rate is too high.
Further, in the method for intermittently skipping the reproduction of voice data, the meaning of the data may not be understood. If voice data contains few silent portions, the method for erasing silent portions is not so advantageous.
As described above, in the conventional methods, since control is performed based on the acoustic features of voice data, it is often difficult to understand reproduced voice data.